全文获取类型
收费全文 | 916篇 |
免费 | 14篇 |
国内免费 | 120篇 |
专业分类
化学 | 869篇 |
晶体学 | 12篇 |
力学 | 3篇 |
综合类 | 1篇 |
物理学 | 165篇 |
出版年
2023年 | 25篇 |
2022年 | 15篇 |
2021年 | 12篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 11篇 |
2017年 | 20篇 |
2016年 | 13篇 |
2015年 | 26篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 69篇 |
2011年 | 32篇 |
2010年 | 44篇 |
2009年 | 56篇 |
2008年 | 40篇 |
2007年 | 65篇 |
2006年 | 72篇 |
2005年 | 54篇 |
2004年 | 55篇 |
2003年 | 42篇 |
2002年 | 35篇 |
2001年 | 29篇 |
2000年 | 17篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 25篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 23篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1966年 | 1篇 |
排序方式: 共有1050条查询结果,搜索用时 46 毫秒
51.
The surface structure of Ce adsorbed on a Mo(110) surface was studied by reflection high energy electron diffraction. Five kinds of surface structures were found with different deposition coverages in the submonolayer region. These structures have a common feature that Ce atoms possess a periodicity with double spacing at the atomic rows in the Mo[
10] direction. Observed at 1 ML of Ce coverage was a surface structure related to a deformed fcc Ce(111) plane. 相似文献
52.
A general and selective method for the direct amidation of secondary benzyl alcohols with both sulfonamides and carbamates is described. This method has been applied to a variety of substrates and the reaction proceeded smoothly at room temperature in the presence of 5 mol % molybdenum(V) chloride to give the desired products in good yields. 相似文献
53.
Molybdenum reacted with diethyldithiocarbamate showed a single line at g=1.980 in electron paramagnetic resonance spectrometry at room temperature after reduction by oxalic acid. Molybdenum in 10 μl of urine could be quantitated within 5 min with the detection limit of 50 pg. 相似文献
54.
火焰原子吸收分析中表面活性剂的增感和抑制干扰作用的机理研究 总被引:9,自引:0,他引:9
证实和补充了文献[1]建立的FAAS分析中表面活性剂的增感机理模型,并对FAAS分析中表面活性剂抑制共存元素干扰的作用和机理作了探讨。表面活性剂能抑制共存元素干扰的主要原因是其胶团能和被测元素的离子或干扰离子形成胶团化物;表面活性剂在火焰中中的不完全燃烧使火焰气体还原性增强,温度升高也是其抑制干扰的因素之一。 相似文献
55.
本文报导了傅里哀变换红外发射光谱法研究多相氧化物催化剂的实验装置的建立及实验条件的考察。设计加工了一个温度范围宽,可在各种气氛和真空条件下原位研究氧化物催化剂的红外发射池。以MoO_3为例,考察了样品厚度,测试温度对发射光谱的影响。当样品量小于1mm·cm~(-2)时,随样品量增加,谱峰强度线性增加,但峰形不发生变化。当样品量高于1mg.cm~(-2)时,随样品量增加,谱图严重畸变。随样品温度升高,谱峰强度近似线性增加。并用该方法研究了MoO_3在还原和再氧化过程中表面氧物种的变化。结果表明桥式MO?O?Mo物种比端基Mo=O物种较易还原,再氧化时,Mo=O物种比Mo?O?Mo物种优先形成。 相似文献
56.
The coupling of visible nanosecond laser pulses to metallic targets irradiated in vacuum is studied. The expressions of the vapour and plasma ignition times are obtained. Two cases for vapour breakdown in the plasma ignition process are considered. The first case is that 40 generations of new electrons are born in vapour generation time before plasma formation as assumed in the literature. The second case is that 10 generations of new electrons are born in vapour generation time. Molybdenum (Mo), niobium (Nb) and aluminium (Al) targets are considered for illustrations of our results. The expression of the plasma ignition time for the Al target is substantially different from that reported in the literature. The vapour and plasma ignition threshold laser intensities are calculated and compared with those reported in the literature. Reasons for disagreement are discussed. The plasma ignition threshold estimated in the second case is noted to be in good agreement with the reported experimental result. 相似文献
57.
Resasco D.E. Alvarez W.E. Pompeo F. Balzano L. Herrera J.E. Kitiyanan B. Borgna A. 《Journal of nanoparticle research》2002,4(1-2):131-136
Existing single-walled carbon nanotube synthesis methods are not easily scalable, operate under severe conditions, and involve high capital and operating costs. The current cost of SWNT is exceedingly high. A catalytic method of synthesis has been developed that has shown potential advantages over the existing methods. This method is based on a catalyst formulation that inhibits the formation of undesired forms of carbon; it can be scaled-up and may result in lower production costs. 相似文献
58.
A photoemission study of molybdenum hexacarbonyl adsorption and decomposition on TiO2(1 1 0) surface
The adsorption and decomposition of molybdenum hexacarbonyl on (1 1 0) TiO2 surfaces were studied using both core levels and valence band photoemission spectroscopies. It was found that after an adsorption at 140 K, when going back to room temperature, only a small part of molybdenum compounds, previously present at low temperature, remained on the TiO2 surface. This indicates that the desorption temperature on such a surface is lower than the decomposition one. The use of photon irradiation to decompose the hexacarbonyl molecule was also studied. It was shown that during such a decomposition molecular fragments were chemisorbed on the surface allowing a higher amount of metal to remain on the surface. It was also shown that it was possible to get rid of adsorbed subcarbonyl groups and to organize the metal atoms by thermal treatments at temperatures as low as 400 K, i.e. much lower than the one needed to obtain the same structures using physical vapour deposition (PVD). Moreover, due to lower used temperatures, this chemical way of deposition allows a better control of the interface than during PVD growth. 相似文献
59.
The dehydration of molybdic acid, MoO3---H2O, was studied by thermal analysis, X-ray diffractometry and FTIR spectroscopy. The results show that an intermediate phase, MoO3-2/3H2O is formed at 216 °C and the monoclinic form of MoO3 is grown above 350 °C. The mechanism of dehydration and structural rearrangement were confirmed by the features of the infrared spectra showing formation of corner-shared MoO6 octahedra. 相似文献
60.
Harry Adams Sarah A Morris Jeffrey C Motley 《Journal of organometallic chemistry》2004,689(3):522-527
Transfer of dithiolene ligands from [Ni(S2C2Ph2)2] to the dimolybdenum complex [Mo2(μ-C2R2)(CO)4Cp2] (R=CO2Me, Cp=η-C5H5) affords the first example of a dithiolene alkyne complex, [Mo2(μ-C2R2)(μ-S2C2Ph2)2Cp2], together with [Mo2(μ-SCRCR)(μ-SCPhCPh)Cp2] in which sulfur transfer from dithiolene to alkyne has occurred. 相似文献